COLD-SENSITIVE E-LYSIS SYSTEMS

The release of recombinant bacteria into the environment is undesirabl e because of possible risks associated with the genetically modified o rganisms, The aim of this study was to establish a cold-sensitive kill ing system with a lethal gene, activated when bacteria encounter lower environmental temperatures. To obtain cold-sensitive lysis vectors, t he lambda cI857 repressor/p(R) promoter expression system was combined with either the lacI/lacZpo or the phage 434 cI/p(R) system that cont rol the expression of the lysis gene E of bacteriophage phi X174. Esch erichia coli strains harbouring such suicide vectors are able to grow at 37 degrees C, but cell lysis takes place at temperatures below 30 d egrees C. By replacing gene E with a beta-galactosidase reporter gene we also showed that the onset of beta-galactosidase activity correspon ds with the onset of lysis at 28 degrees C, Results indicate that thes e newly combined promoter/repressor systems can also be used to confer cold-sensitive expression to any gene of interest. (C) 1998 Elsevier Science B.V. All rights reserved.